For some time, as shown in Patent Document 1, float switches have been known in which the float switch is disposed on the upper portion inside a reservoir tank for supplying flush water to a flush toilet, such that when the water level reaches a full level during water supply, the float switch senses that the flush water level has reached the full level and causes supply of flush water to be stopped.
As shown in Patent Document 1 (Japanese Patent Unexamined Publication No. 2010-236202) and Patent Document 2 (Japanese Patent Unexamined Publication No. 2001-323540), a float switch for detecting the water level in a reservoir tank comprises a base portion attached to the reservoir tank, a support shaft extending from the base portion, and a float for moving up and down along this support shaft.
However, in the above-described conventional float switch, the problem arose that motion of the float, which is movable along the support shaft, could become unstable, such that the flush water level could not be reliably sensed.
For example, if the float switch and the support shaft are in a static state while in contact, the problem may arise that a static frictional force is produced between the float switch float and the support shaft, such that the float does not move relative to the support shaft even if the flush water level reaches the full level during water supply, resulting in non-activation of the float switch, or delay in the activation timing thereof. Another potential problem occurs when air bubbles adhere to the float switch float or the support shaft, interfering with the movement of the float, such that the flush water level during water supply fails to move relative to the support shaft, and the float switch is not activated, or the activation timing thereof is delayed.